/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.web.accept;

import org.springframework.http.MediaType;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
import org.springframework.web.context.request.NativeWebRequest;

import javax.servlet.ServletContext;
import java.util.Map;

/**
 * An extension of {@code PathExtensionContentNegotiationStrategy} that uses
 * {@link ServletContext#getMimeType(String)} as a fallback mechanism when
 * matching a path extension to a media type.
 *
 * @author Rossen Stoyanchev
 * @since 3.2
 */
public class ServletPathExtensionContentNegotiationStrategy extends PathExtensionContentNegotiationStrategy {

    private final ServletContext servletContext;


    /**
     * Create an instance with the given extension-to-MediaType lookup.
     *
     * @throws IllegalArgumentException if a media type string cannot be parsed
     */
    public ServletPathExtensionContentNegotiationStrategy(
            ServletContext servletContext, Map<String, MediaType> mediaTypes) {

        super(mediaTypes);
        Assert.notNull(servletContext, "ServletContext is required!");
        this.servletContext = servletContext;
    }

    /**
     * Create an instance without any mappings to start with. Mappings may be
     * added later on if any extensions are resolved through
     * {@link ServletContext#getMimeType(String)} or through the Java Activation
     * framework.
     */
    public ServletPathExtensionContentNegotiationStrategy(ServletContext servletContext) {
        this(servletContext, null);
    }

    /**
     * Look up the given extension via {@link ServletContext#getMimeType(String)}
     * and if that doesn't help, delegate to the parent implementation.
     */
    @Override
    protected MediaType handleNoMatch(NativeWebRequest webRequest, String extension) {
        MediaType mediaType = null;
        if (this.servletContext != null) {
            String mimeType = this.servletContext.getMimeType("file." + extension);
            if (StringUtils.hasText(mimeType)) {
                mediaType = MediaType.parseMediaType(mimeType);
            }
        }
        if (mediaType == null || MediaType.APPLICATION_OCTET_STREAM.equals(mediaType)) {
            MediaType superMediaType = super.handleNoMatch(webRequest, extension);
            if (superMediaType != null) {
                mediaType = superMediaType;
            }
        }
        return mediaType;
    }

}
